Well, I'm not sure if there are players that can compete with Cowon as equal, I would prefer one of them.
X7 looks a little bit bulky, however, I'll consinder it and i10 as a possible choice, since my prev player was M5L.
Minimum space —32Gb + microSD slot, or 64 Gb without slot. Some sort of last.fm scrobbling would be nice. Wi-fi can be added as some sort of nice little feature, but it's completely not must-have.